
function loadJSON(filename, callback) {
    var xobj = new XMLHttpRequest();
        xobj.overrideMimeType("application/json");
    xobj.open('GET', filename, true);
    xobj.onreadystatechange = function () {
        if (xobj.readyState == 4 && xobj.status == "200") {
            // Required use of an anonymous callback as .open will NOT return a value but simply returns undefined in asynchronous mode
            callback(xobj.responseText);
        }
    };
    xobj.send(null);  
}    

